Trigger controlled oscillator



May 22, 1951 w. A. MILLER TRIGGER CONTROLLED OSCILLATOR Filed Aug. 6,1946 T2? CR YSTAL WILLIAM A. MILLER BY )k/mw ATTORNEY Patented May 22,1951 TRIGGER CONTROLLED OSCILLATOR William A. Miller, Port Jefferson, N.Y., assignor to Radio Corporation of America, a corporation of DelawareApplication August 6, 1946, Serial No. 688,742

9 Claims.

This invention relates to improvements in trigger-controlled oscillatorsand has for one of its objects, to provide a trigger-controlledoscillator in which the time delay or phase between the triggering orinitiating pulse and the start of oscillations in the output of theoscillator remains constant regardless of the random character of thetriggering pulse.

Trigger-controlled oscillators of the invention have munerous uses insystems wherein it is desirable to provide a source of standardfrequency which is controllable and which may be started and stoppedeasily; for example, in time-lapse measuring instruments (intervaltimers) and in frequency-shift keying systems. One application of thepresent invention is in a frequencykeying system such as is described inmy copending application, Serial #591,730 filed May 3. 1945, now U. S.Patent 2,491,387 granted December 13, 1949.

' A more detailed description follows in conjunction with a drawingwherein Figs. 1, 2 and 3 illustrate three different embodiments of thepresent invention.

Throughout the figures of the drawing, the same parts are represented bythe same reference numerals.

Referring to Fig. 1, there is shown a trigger circuit comprising a pairof vacuum tube electrode structures VI and V2 shown in separateenvelopes, although it should be understood that if desired, bothelectrode structures may be located in the same evacuated envelope. Thetwo tubes VI and V2 are unsymmetrically biased; The grid and anodeelectrodes of both tubes VI are connected regeneratively: The :anode oftube VI is connected to the grid of tube V2 through a condenser C2'while the anode of tube V2 is connected to the grid of tube Vl througha resistor-shunt condenser arrangement R2, C3. Tube V I is normallynon-conducting in the absence of an initiating pulse applied to itscathode, while tube V2 is normally conducting. Tube VI is normallybiased to cut-off by means of sourceE. This condition of operationwherein tube V l is normally non-conducting and tube V2 normallyconducting is called the stable state. In the active or non-stable statewhich begins when a tripping negative pulse of sufficient magnitude isapplied to lead I0, the current passing conditions of tubes VI and V2are reversed from that just described. After an interval of time in thisactive state, depending in part upon the time constants of the condenserC2 and resistor RI, the trigger will restore itself to the stable state.

It will be seen that the trigger circuit has only one degree ofelectrical stability. It should. be noted that the cathode of the tubeVI has in circuit therewith, a resistor R4 which is shunted by a diodeDI. This resistor may be of relatively high value. The diode DI is anopen circuit for the negative initiating pulse to be applied to leadIf]. The use of the diode and resistor RA in the location shown, enablesthe quick dissipation of the negative input pulse which initiates theactive period of the trigger circuit, and thus obviates any eiiect theduration of the input pulse might have had on the trigger circuit duringits active state. The condenser C3 which is of relatively small size isused across resistor R2 in order to hasten the change over from oneconductive state to the other.

Coupled to the trigger circuit is a Hartley type of oscillatorcomprising a, vacuum tube V3 having a main tank circuit LI, CI. The tankor tuned circuit LI, Cl is connected between the cathode of tube V2 ofthe trigger circuit and ground. Different points on the inductancecoilLI are connected to the grid and cathode of tube V3. Connected betweenthe anode of tube V3 and the positive terminall3+ of a source of anodepolarizing potential, is an output tuned circuit L3, C4. A bypasscondenser C5 is provided between ground and terminal 3+ for pro-vidingalow A. C. impedance to ground, thus preventing interaction or feedbackfrom one vacuum tube to the other. This tuned circuit L3, C4 is tuned tothe frequency of oscillation but has substantially little efie'ct on thefrequency of the oscillator. For the lower frequencies, the tunedcircuit L3, C4 can be replaced by a resistor while at the higherfrequencies of oscillation, this tuned cir; cult can be replaced by aninductance coil (choke).

During the time the trigger circuit VI, V2 is in the stable state, thetube VI will be non-cor ductive and the tube V2 conductive. In thiscondition, the tuned circuit Ll, Cl which is the main tank circuitcontrolling the frequency of oscillation of the oscillator tube V3; iseffectively shunted to ground by a low resistance composed primarily ofthe D. C. resistance of tube. V2 in series with the anode resistor R3.In this condition wherein tube V2 is conductive and shunts the tankcircuit LI, CI, the generation of oscillations is preventedin theoscillator V3. soon as a negative tripping pulse is impressed on lead I0of such magnitude as to cause tube VI to conduct and V2 to ceaseconducting (that is, change the trigger circuit from the stable state tothe active state), then cessation of current through tube V2 removes thelow resistance shunted across the main tank circuit Ll, Cl and enablesthe oscillator V3 to generate oscillations. This oscillator willcontinue to generate oscillations with a period determined by the timeconstants of Li, Cl (also, to a small extent, by the tuning of tankcircuit L3, C4) until such time as the trigger circuit returns to itsnormal or stable state.

I have thus been able to provide an output sine wave whose phase is heldconstant with respect to the initiating or tripping pulse applied to thetrigger circuit, regardless of the random character of the triggering orinitiating pulses.

Fig. 2 is a modification of the system of Fig. 1

wherein a crystal C is used to control the frequency of oscillations ofthe oscillation generator, thus enabling the oscillator to producepulses of radio frequency energy in response to triggering input pulses.These radio frequency pulses consist of sections of as accurate a sinewave as the crystal C will permit. The length of the Wave train from theoscillator follows the length or width of the trigger output pulses andis under control of the operator or attendant controlling the durationof the trigger output pulses. Fig. 2 operates in substantially the samemanner as does Fig. 1 except for the crystal-control feature. Fig. 3 isa still further modification and shows a trigger circuit V! and V2 whichrequires a triggering pulse to change the states of conduction of thetwo tubes V'l and V2 and a second pulse to restore the trigger circuitto its original state. Putting it in other words, if tube Vl isconductive and tube V2 non-conductive, a tripping input pulse to leadIt) will cause tube V'l to conduct and tube V2 to cease conducting byvirtue of the regenerative cross connections between the grids andanodes of the two tubes, while a second pulse is required to cause tubeV2 to conduct and V! to cease conducting. The trigger circuit Vl and V2thus has two degrees of electrical stability and operates in a manneranalogous to a locking circuit. It should be understood, however, thatthis trigger circuit Vl and V2 is not a free running multivibrator.

The sine wave oscillator V3 which may be either of the form shown inFig. l (self-excited) or of the form shown in Fig. 2 (crystalcontrolled) thus has its times of initiation and termination (start andstop) externally controlled.

The bias on tube Vl is provided by the resistor Rl2, and this bias neednot be nearly great enough to cause tube V! to be cut off due to thebias voltage but need be only great enough to insure that at the timewhen the potentials are first applied to the equipment, that tube V'lwill tend to draw less current than tube V2. This condition assures thefact that initially tube V'I will be non-conducting and tube V2conducting at the start of operations.

In the operation of the system of Fig. 3, assuming that at the starttube VI is non-conductive and tube V2 conductive, the application of atriggering pulse of positive polarity to lead will cause tube VI to turnon (become conductive) and tube V2 to turn ofi (become non-conductive).These tubes will remain in this condition until another positive pulseis applied to the lead I0. When this second positive pulse is applied tolead [0, the grid of tube V2 will go positive as a result of which thetube of V2 will turn on (become conductive) and tube V! turn off (becomenon-conductive). The trigger circuit will then remain in this lastcondition until another positive triggering pulse reverses the states ofconduction of the two triggering tubes. This mode of operation of thetrigger circuit V'l and V2 will also occur though in a slightlydifferent manner if only negative triggering pulses are applied to leadl0. Assuming that tube V'l is turned ofi and tube V2 turned on, then anegative triggering pulse to lead It will turn tube V2 off and turn tubeV'l on due to the regenerative cross connections. The triggering circuitwill remain in this condition until the next negative triggering pulseis applied to lead II] which will turn tube V'l oil and V2 on.

The ready position for operation of trigger circuit is tube V! turnedoff and tube V2 turned on. The bias E in Fig. 3 drops the potential ofthe grids of tubes Vl and V2 below ground.

When tube V2 is turned off (non-conductive), the oscillator V3 willstart oscillating because of the removal of the low resistance shuntpath from the tank circuit Ll, CI. When tube V2 conducts, the oscillatorV3 will not oscillate by virtue of the low resistance shunt across themain oscillator tank circuit LI, Cl.

What is claimed is:

l. A trigger-controlled oscillator system comprising a pair of vacuumtube electrode structures each having an anode, a cathode and a grid,cross-connections between the anodes and grids of said electrodestructures for regeneratively connecting said structures together,whereby the flow of maximum current through one tube is accompanied bythe flow of minimum current through the other tube, and vice versa, andan oscillation generator circuit including an electron discharge devicehaving a frequency determining element in the cathode circuit of one ofsaid electrode structures, whereby the flow of current through said oneelectrode structure provides a shunt path for said frequency determiningelement, thereby preventing oscillations from being produced in saidoscillation generator, said discharge device having an output tunedcircuit separate and apart from said frequency determining element, andmeans for deriving alternating current output energy from said outputcircuit.

2. A trigger-controlled oscillator system comprising a pair of vacuumtube electrode structures each having an anode, a cathode and a grid,cross-connections between the anodes and grids of said electrodestructures for regeneratively connecting said structures together,whereby the fiow of maximum current through one tube is accompanied bythe flow of minimum current through the other tube, and vice versa, andan oscillation generator circuit having a frequency determining elementin the space current path of one of said electrode structures, wherebythe state of conduction of said one electrode structure controls theoperativeness of said oscillation generator, said oscillation generatorcircuit including an electron discharge device having a controlelectrode and an anode, a connection from said control electrode to saidfrequency determining element, means for deriving alternating currentoutput energy from said anode, and a circuit for applying a pulse ofsuch polarity and magnitude to one of said electrode structures as toreverse the states of conduction of said pair of electrode structures.

3. A trigger-controlled oscillator system comprising a pair of vacuumtube electrode structures each having an anode, a cathode and a grid,crossconnections between the anodes and grids of said electrodestructures for regeneratively connecting said structures together,whereby the flow of maximum current through one tube is accompanied bythe flow of minimum current through the other tube, and vice versa, andan oscillation generator having a frequency determining reactanceelement in the space current path of one of said electrode structures,whereby the state of conduction of said one electrode structure controlsthe operativeness of said oscillation generator, and a circuit forapplying a pulse of such polarity and magnitude to one of said electrodestructures as to reverse the states of conduction of said pair ofelectrode structures, said oscillation generator also having in circuittherewith a tuned circuit separate and apart from said reactance elementfor developing alternating current output energy.

4. A trigger-controlled oscillator system comprising a pair of Vacuumtube electrode structures each havin an anode, a cathode and a grid,cross-connections between the anodes and grids of said electrodestructures for regeneratively connecting said structures together,whereby the flow or" maximum current through one tube is accompanied bythe flow of minimum current through the other tube, and vice versa, andan oscillation generator having a pair of parallel tuned circuits one ofwhich is a determining circuit in the space current path of one of saidelectrode structures and the other of which is an output circuitdeveloping alternating current energy, whereby the state of conductionof said one electrode structure controls the operativeness of saidoscillation generator, and a circuit for applying a pulse of suchpolarity and magnitude to one of said electrode structures as to reversethe states of conduction of said pair of electrode structures.

5. In a signalling system, an electron discharge device havingelectrodes regeneratively coupled by a circuit which includes areactance, for the production of oscillatory energy, a pair of electrondischarge tubes each having an anode, a cathode and a control electrode,impedances cross-coupling the anodes and control electrodes of saidtubes, a source of unidirectional current connected by impedancesbetween the anode and cathode of each tube, the arrangement being suchthat when current flow is started through one tube the other tube isbiased to cut-01f and vice versa, leads coupling the impedance betweenelectrodes of one of said tubes in shunt to a portion at least of saidreactance of said device, the space path of said device beingindependent of the cross-coupling circuit of said pair of tubes, andmeans for applying the control potential to an electrode other than theanode of one of said tubes for reversing the conduction states of saidtubes.

6. In combination, a self-restoring trigger circuit comprising a pair ofelectron discharge devices coupled together regeneratively to have onedegree of electrical stability, whereby one device is normallyconductive and the other device normally non-conductive in the stablestate, and vice versa in the active state of the trigger circuit, anoscillation generator having an electron discharge device whose spacepath is independent of the regenerative coupling between said first pairof devices, said generator having a frequency controlling reactanceelement in the space current path of one of said devices, and a lead forsupplying control pulses to said trigger circuit of such polarity andmagnitude as to trip said trigger circuit from the stable to the activestate.

7. In combination, a trigger circuit comprising a pair of electrondischarge devices each having an anode, a cathode and a grid, impedancescrosscoupling said anodes and grids in regenerative manner, biasconnections for said devices whereby when one device is conductive, theother device is non-conductive and vice versa, a resistor across thegrid and cathode of one of said devices, a connection for supplyingtriggering pulses to said trigger circuit, and an oscillation generatorhaving a frequency controlling element in the space current path of saidone device, said oscillation generator including an electron dischargedevice whose space path is independent of the regenerative couplingbetween said pair of devices.

8. A trigger-controlled oscillator comprising a pair of electrondischarge device structures each having an anode, a cathode and a grid,resistors cross-coupling said anodes and grids, a pair of condensersconnected between said grids, a lead for supplying triggering pulses tothe junction point of said condensers, individual resistors from saidgrids to a common source of negative biasing potential, whereby onestructure is conductive and the other structure non-conductive, and viceversa in response to a triggering pulse, and an oscillation generatorhaving a parallel tuned circuit a portion of which at least is in thespace current path of one of said structures, said oscillation generatoralso having another tuned circuit across which alternating currentoutput energy is developed.

9. The combination with a trigger circuit having a pair of electrondischarge device electrode structures regeneratively coupled together sothat when one structure is conductive, the other is non-conductive andvice versa, of an oscillation generator having a pair of tank circuitsat least a portion of only one of which is in the space current path ofone of said structures, whereby the operativeness of said oscillationgenerator is controlled by the conductivity of said one structure.

WILLIAM A. MILLER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,266,668 Tubbs Dec. 16, 19412,272,070 Reeves Feb. 3, 1942 2,273,193 Heising Feb. 17, 1942 2,370,685Rea March 6, 1945 2,434,400 Easton Jan. 13, 1948 2,442,769 Kenyon June8, 1948 2,443,619 Hopper June 22, 1948 2,445,448 Miller July 20, 1948OTHER REFERENCES Electronics, June 1946-pages 126, 128. Radar SystemFundamentals-War Dept, TM-11-466 December 1943, pages 187-191.

